Jason Carter just missed reaching double figures in his first career start for Xavier (2-0). He finished with a career-high nine points.
The Musketeers led by as many as 27 points in the second half.
Elijah Burns scored 19 points and Jalen Pickett added 18 to lead Siena (1-1).
Jones needed just 20 minutes to score his 20 points, two short of matching his career high. He had 12 in the first half, eight on four crowd-pleasing dunks. He ran downcourt celebrating with the “raise the roof” gesture after the third dunk.
After committing turnovers on their first three possessions, the Musketeers capitalized on Siena’s poor shooting. Siena went 1 for 11 from the field in one stretch, while Xavier put together a 14-1 run and took a 26-16 lead with 6:03 left in the first half.
Siena has lost its last 10 games against Big East teams since beating Villanova, 74-59, on March 18, 2003, in the NIT.
Xavier has won its last four games against Siena to improve to 4-1 in the series.
Siena: Hosts St. Bonaventure on Monday.
Xavier: Hosts Missouri on Tuesday in the third of four season-opening home games.